This invention relates to inventory control systems in general, and in particular to an improved inventory control system using R.F. object identification.
Inventory control systems are used generally to keep track of items (xe2x80x9cobjectsxe2x80x9d) in a collection of items. For example, an automobile parts warehouse at any given time has a collection of vehicle parts (xe2x80x9cobjectsxe2x80x9d) in inventory. The kind and number of such parts varies every day, as currently inventoried parts are sold and new parts are received. In order to keep track of the number and kind of vehicle parts in inventory, some type of inventory control system must be used. Similarly, in a semiconductor manufacturing operation, at any given time there is a collection of integrated circuits (xe2x80x9cobjectsxe2x80x9d) of one or more types located somewhere in the facility, which must be accounted for using an inventory control system. Similar requirements exist for containerized shipping operations and other warehousing and manufacturing operations. In most airports, there is a requirement for keeping track of luggage and articles in transit through the system, from the hands of a passenger or messenger arriving at the airport to the final destination of the luggage or article.
In all examples of known inventory control systems, either the containers for the different objects or the objects themselves (or both) are usually provided with some type of human readable or machine readable identification indicia, such as a label or tag affixed to the object or the container. In more sophisticated systems, a computer is used to assist in keeping track of the objects. When an object is removed from the actual location, or passes from one location to another, some procedure is typically used to note the fact that the location status of the object has changed. This is accomplished either by operator entry of the change into a manual log or the system computer, or by using tag or label reading devices (e.g., bar code readers) to enter the information into the system computer. All known inventory control systems suffer from several disadvantages. For example, once a new item has been tagged, the current location of that item must be entered into an inventory list, either manually or automatically. Manual entry of the location and correlation of the location with the specific item is subject to human error. Automatic entry of such information requires a label or tag reader either at the location itself, or some way of verifying that the item identification and associated location information are correct. In addition, when an item is removed from a current location, some arrangement must be made to ensure that this change of inventory status is noted in the master list, again either manually or automatically. Automatic systems using coded marker tags or labels are also subject to erroneous code reading due to contamination or obliteration of the coded markings or even partial obscuring of these markings due to rough handling procedures. Perhaps most importantly, current inventory control systems do not provide a simple and efficient way to find a desired object stored somewhere in a large collection of different objects, such as inventoried items in a large warehouse or manufacturing facility.
The invention comprises an inventory control system which is devoid of the above-noted limitations and disadvantages, which can be implemented using objects and object containers of any physical size and shape, which can be installed in any inventory storage facility regardless of size, and which has several features absent from known inventory control systems.
In a broadest aspect the invention comprises an inventory control system which uses R.F. sensitive circuits to maintain inventory control of all objects in a collection of objects. Each object has an associated R.F. sensitive circuit which resonates at a specific frequency unique to that class or genus of objects when an R.F. signal at that particular frequency is received by the circuit, and a transmitter for generating an acknowledgement signal to an inventory control reader for identifying the object and the present location of the object.
The circuit also includes a unique identifier, such as a multi-digit number or a set of alphabetic or alpha numeric characters, stored in a non-volatile memory, which serves to identify that particular item in a collection of like items. Thus, for example, in an automotive parts warehousing installation, all carburetors of a particular type are assigned a particular frequency, and each individual carburetor is assigned a different identifier. The circuit draws power from the R.F. carrier signal, when received, which eliminates the need for any discrete power source for each object circuit.
The R.F search signals are generated by an R.F. signal generator which produces a digitally modulated R.F. carrier signal. The frequency of the carrier signal specifies the class of object being sought, while the identity of the specific object is specified by the digital modulation of the carrier. The frequency of the R.F. carrier can be varied over a range of frequencies which cover all classes of objects in a given inventory control system. The R.F. carrier may be modulated using either amplitude modulation or on-off carrier modulation. In addition, the R.F. carrier signal contains the energy used to power the individual circuits associated with the objects in the inventory, so that no power source (such as a battery) is required for the individual object circuits. The generator is preferably controlled by a computer having the appropriate application programs to implement the system.
The location of a given object is determined in the following manner. The inventory space is virtually partitioned into elemental three-dimensional compartments, which may correspond to the real storage compartments in the inventory space. One or more transmitter coils are physically positioned at each elemental compartment. The R.F. signals are sequentially applied to the transmitter coils for each compartment using an ordered scanning arrangement. In the preferred embodiment, each set of transmitter coils associated to a particular elemental compartment is connected to one output node of a multiple output node scanning switch. The input node of the scanning switch is coupled to the output of the R.F. generator. In operation, the R.F. generator is activated and the R.F. output signals are sequentially applied to each output node of the scanning switch. When an object circuit detects the correct frequency and identifier, the object circuit generates an acknowledgement signal, which is detected by an R.F. identification reader located in or near the compartment containing the acknowledging object circuit. The reader conveys the detect condition to the system computer, which matches the detect condition with the elemental compartment location of the currently active R.F. transmitter coils. In this way, both the physical presence and the location of the object being sought are determined.
The system may also be operated to perform an inventory check for all objects of a given class, or a complete inventory check to test the integrity of the inventory control system. For example, to check the location of all objects of a given class, the R.F generator is activated at the specific frequency for that class of objects (e.g., carburetors) and the specific frequency carrier signal is sequentially modulated with all object identifiers. The resulting R.F. signals are sequentially applied to each set of elemental compartment location coils, and a list is compiled in the system computer of all detect conditions and locations. This list may then be compared with a previously created master list and any discrepancies may be noted and investigated. To check for individual objects of a given class, the R.F. carrier signal of the proper frequency is generated, and this carrier is digitally modulated with the identifiers of the objects being sought, using a previously created master list. The desired master lists may be created by sequentially applying a complete set of digitally modulated R.F. signals at all the frequencies of interest to each set of transmitter coils in the inventory space, and noting the identifiers and locations when detect conditions are obtained.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.